Saturday, May 08, 2010

Windy sunset

kw: photographs, photography, nature

The nice thing about wind at sunset is that the clouds move, so the view changes frequently. The trouble with wind at sunset is that the clouds move, which causes jitter in HDR images. I'll be teaching photography classes this Summer, and there is always demand for learning special techniques such as HDR. Sunsets are good for that, and I knew a cloudy, windy day would probably have a nice sunset. I popped over to a wildlife refuge in New Castle County to see if I could get a few example image sets.

By the way, HDR, for High Dynamic Range, ought to be called CDR, for Compressed Dynamic Range, because that is actually what you are doing. You are bringing in the washed-out highlights and the blacked-out lowlights to show more of the details the eye can see better than a one-image camera can. The software I use is EasyHDR Basic (the free version). My camera can exposure compensate beyond the +2EV/-2EV limit of most cameras, so I tried one image with five exposures (-3EV, -1.3EV, 0, +1.7EV, +3EV) and the software did its thing just fine. I won't be showing that here, though, but two of the 3-image (-2,0,+2) sets and singles for comparison.

Early on, just after the Sun moved behind the bar of clouds near the horizon, I shot a series that included this, which the camera tells me is its best exposure. One has to peer closely to see any detail in the nearly black foreground, and the reddish area below the clouds is washed out.

I optimized this HDR image to emphasize the sky colors, so the foreground is still rather dark. However, the red area below the clouds shows up much better. Note that the clouds look "stuttery" compared to the first image. That is due to cloud motion between shots. The wind was 40+mph at ground level; there's no telling how fast the clouds were moving!

Here is a zoomed-in image, a single again, with the Sun just peeking through the trees. The light meter in the camera was pointed at the sky above the clouds. I like this image. Let's see if HDR can do better.

This is closer to what I could see, though still not quite what I'd like. The red area is very nice, more balanced, and the sky looks good. It is pretty hard to get the foreground to show anything. The car in this image was in just one of the images used for this composite.

OK, one more bit of tinkering. I cropped a chunk out of the middle of the prior image and boosted the lowlights a little with the "brighten" function in Irfanview. There is little detail in the clouds, so the image still lacks something. It might benefit from a heavy dose of Unsharp Masking, which Gimp can do (also Photoshop, but Gimp is free), but at this point, it is probably better to await the next pretty sunset.